Dual-Circularly Polarized X-Band Isoflux Antenna for LEO Payload Telemetry Applications

This paper presents the design, simulation, and performance evaluation of an X-band isoflux antenna operating in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8.0-8.4 \text{GHz}$</tex> frequency band, intended for near-Earth satellite and high-altitude airborne communication systems. Isoflux antennas are essential in applications where uniform power flux density across the visible Earth disk is required, particularly compensating for slant-range losses at oblique incidence angles. The proposed design employs a WR112 waveguide-fed structure with an integrated septum polarizer to support dual circular polarizations, a dielectric conical element to facilitate the isoflux profile, and corrugated rings to enhance beam uniformity near the horizon. Full-wave electromagnetic simulations confirm return losses better than -21dB and inter-port isolation exceeding 20 dB. The radiation pattern exhibits a flat gain response within <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 1 ~\text{dB}$</tex> across the coverage area, validating the antenna's suitability for uniform Earth coverage. Compact structural dimensions and robust